Electrochemical oxidation of acetaminophen and its transformation products in surface water: effect of pH and current density

Photo-electrocatalytic based removal of acetaminophen: Application of visible light driven heterojunction based BiVO4/BiOI photoanode

The presence of organic micro-pollutants (OMPs) in wastewater treatment effluents is becoming a major threat to the water safety for aquatic and human health. Photo-electrocatalytic based advanced oxidation process (AOP) is one of the emerging and effective techniques to degrade OMPs through oxidative mechanism. This study investigated the application of heterojunction based BiVO₄/BiOI photoanode for acetaminophen (40 μg L^-1) removal in demineralized water. Photoanodes were fabricated by electrodeposition of BiVO₄ and BiOI photocatalytic layers. Optical (UV-vis diffusive reflectance spectroscopy), structural (XRD, SEM, EDX) and opto-electronic (IPCE) characterization confirmed the successful formation of heterojunction for enhanced charge separation efficiency. The heterojunction photoanode showed incident photon to current conversion efficiency of 16% (λ_max = 390 nm) at an external voltage of 1 V under AM 1.5 standard illumination. The application of the BiVO₄/BiOI photoanode in the removal of acetaminophen at 1 V (external bias) vs Ag/AgCl under simulated sunlight showed 87% removal efficiency within the first 120 min compared to 66% removal efficiency of the BiVO₄ photoanode. Similarly, combining BiVO₄ and BiOI exhibited 57% increase in first order removal rate coefficient compared to BiVO₄. The photoanodes also showed moderate stability and reusability by showing 26% decrease in overall degradation efficiency after three cycles of each 5 h experiment. The results obtained in this study can be considered as a stepping stone towards the effective removal of acetaminophen as an OMP present in wastewater.

Improved degradation of tetracycline antibiotic in electrochemical advanced oxidation processes (EAOPs): bioassay using bacteria and identification of intermediate compounds

Among the pharmaceutical compounds, tetracycline is the second most common group of antibiotics in terms of production and consumption worldwide, which their entrance in to hospital, domestic and industrial wastewaters pollute water sources and environment and finally leads to antibiotic resistance. The aim of this study was to determine the efficiency of electrochemical processes, Fenton, electro-Fenton (EF) and sono-electro-Fenton (SEF) separately and using Graphite (G)/β-PbO2 anode to remove tetracycline from aqueous solutions. First, experiments for the electrochemical process by the response-surface methodology (RSM) using variables including pH (3–9), initial tetracycline concentration (20–100 mg/L), electrolysis time (4–45 min) and current density (0.5–4.5 mA/cm2) was designed and the optimal conditions of these variables were 3.5, 25.6 mg/L, 42.6 min, and 1.98 mA/cm2, respectively. Under the optimal conditions of the electrochemical process, the effect of FeSO4 with values of 0.02-0.08 g/250 mL in the Fenton process and the effect of H2O2 of 0.05–0.5 mg/L in the EF process were investigated, and the optimal values of 0.06 g/250 mL and 0.2 mg/L was obtained for FeSO4 and H2O2, respectively. Under optimal conditions, the removal efficiencies of SEF, EF, sono-electrochemical (SEC), electrochemical, Fenton and ultrasonic processes were 98.8%, 93.6%, 87.9%, 81.3%, 71.6%, and 11.5%, respectively. G/β-PbO2 anode had only 37.5% higher removal efficiency than graphite anode. Under the optimal conditions of SEF process, changes in toxicity reduction by bioassay with E. coli and Staphylococcus aureus bacteria were 86% and 58.4%, respectively, and the kinetic study showed that the removal of tetracycline by SEF process with R2=0.9975 followed the pseudo-first-order kinetics. Finally, intermediate compounds obtained from tetracycline analysis were identified using LC-MS analysis.

Medicines as an emergent contaminant: the review of microbial biodegration potential

Emerging environmental contaminants, such as medicine waste, are of great concern to the scientific community and to the local environmental and health departments because of their potential long-term effects and ecotoxicological risk. Besides the prolonged use of medicines for the development of modern society, the elucidation of their effect on the ecosystem is relatively recent. Medicine waste and its metabolites can, for instance, cause alterations in microbial dynamics and disturb fish behavior. Bioremediation is an efficient and eco-friendly technology that appears as a suitable alternative to conventional methods of water waste and sludge treatment and has the capacity to remove or reduce the presence of emerging contaminants. Thus, this review has the objective of compiling information on environmental contamination by common medicines and their microbial biodegradation, focusing on five therapeutic classes: analgesics, antibiotics, antidepressants, non-steroidal anti-inflammatory drugs (NSAIDs), and contraceptives. Their effects in the environment will also be analyzed, as well as the possible routes of degradation by microorganisms.

Dicyandiamide-assisted HKUST-1 derived Cu/N-doped porous carbon nanoarchitecture for electrochemical detection of acetaminophen

MOFs-derived metal/carbon materials have been considered as promising candidates for the electrochemical detection of micropollutants. However, the aggregation of metal nanoparticles and structure collapse of precursor MOFs during pyrolysis significantly hamper the improvement on detecting performance. Herein, a dicyandiamide-assisted strategy is utilized to synthesize well-dispersed Cu/N-doped porous carbon nanoarchitecture (CuNC) for the electrochemical detection of acetaminophen (AP). The constructed CuNC sensor exhibits excellent electro-analytical performance for monitoring AP with linear range from 0.01 μM to 921.2 μM, and the low detection limit of 2.46 nM (S/N = 3). The improved performance of CuNC sensor is ascribed to the introduction of dicyandiamide, which can prevent HKUST-1 framework breakage and reduce the aggregation tendency of Cu, leading to the evenly distributed small Cu nanoparticles, abundant N species, hierarchical channel structure, and high conductivity carbon framework. These advantages endow predominant repeatability, stability, and selectivity of CuNC sensor. This strategy provided a novel approach to preparing MOFs-derived carbon nanoarchitectures with excellent electroanalysis performance to monitor micropollutants.